▎ 摘　　要

In this paper, a broadband and tunable terahertz polarization converter metasurface is proposed, which is composed of an open metal ring embedded with graphenes and a columnar metal on polyimide (PI) dielectric-metal substrate. The polarization conversion rate (PCR) converted to cross-polarized in reflection mode can be regulated from 95% to 20% in a wide band from 2.1 to 3.6 THz by adjusting the Fermi energy of graphene. Simulation results show that broadband polarization conversion results from three resonances in neighboring frequencies, and the physical mechanism underlying tunable function is explained by the distribution of surface current in different states. In addition, the reflection coefficient and reflection phase in orthogonal component are calculated to further reveal basic principle of proposed polarization converter. This study could continue the process of developing compact and active polarization and wave front control application in the THz, and may be applied in various areas such as wireless communication, terahertz sensing and imaging.